A damper of such type is generally equipped with a hub-side flange and a flywheel-side side plate body which houses the foregoing flange by covering both sides and outer peripheral side of the flange, and has a damper mechanism for developing a torsional torque between the flange and the side plate body. A notch 20 is formed on an outside end of the flange 2 as shown in FIG. 5, and liquid is filled in liquid chambers (28 & 29) formed by the notch 20 and an inside face of the side plate body. A projection 27, which protrudes in the liquid chambers (28 & 29) to partition the chambers into front and rear divided-chambers 28 & 29 in a rotation direction, is formed on the inside face of the side plate body 3 and a main choke A1 connecting the both divided-chambers 28 & 29 is formed.
In order to let a hysteresis torque change in two stages for example, a stepped part 60 is formed on a midway of the notch 20 so that, when the side plate body 3 is twisted relatively to the flange 2 from a state of FIG. 5 for example to a rotation direction R side by .theta.1 or to an opposite to the ration direction R side by .theta.2, a clearance of the choke A1 is changed from d1 to d2 and the hysteresis torque is increased from H1 to H2 as shown by FIG. 6.
However, in the event when such a structure as changing the hysteresis torque by only the torsion angle of the side plate body 3 relative to the flange 2 is employed, it becomes impossible to develop the small hysteresis torque H2 in response to circumstances in a large torsion angle range and further it becomes impossible to develop the large hysteresis torque in response to circumstances in a small torsion angle range.